Output signal error detection, circumvention, signal reconstruction and recovery

ABSTRACT

A method of dealing with anomalies in an output signal is provided. The method includes monitoring transitions in the output signal. When transitions do not occur at expected times, detecting an anomalous signal. Determining the type of anomalous signal based at least in part on the time period of the anomalous signal and conditioning the output signal based on the type of anomalous signal detected.

GOVERNMENT CONTRACT RIGHTS

The U.S. Government may have certain rights in the present invention asprovided for by the terms of Government Contract # DASG60-00-C-0072under program THAAD.

BACKGROUND

Devices that include integrated circuits that generate output signalsare prone to have issues when exposed to shock or vibrationenvironments. In particular, during a shock occurrence anomalous outputscan occur which can result in system level errors that are unacceptable.An example of a device that is subject to shock or vibrationenvironments is an accelerometer placed in a missile. The reliance onanomalous accelerometer data by an inertial system of the missile canresult in a catastrophic failure.

For the reasons stated above and for other reasons stated below whichwill become apparent to those skilled in the art upon reading andunderstanding the present specification, there is a need in the art foran effective method of dealing with anomalous outputs of integratedcircuits.

SUMMARY OF INVENTION

The above-mentioned problems of current systems are addressed byembodiments of the present invention and will be understood by readingand studying the following specification. The following summary is madeby way of example and not by way of limitation. It is merely provided toaid the reader in understanding some of the aspects of the invention. Inone embodiment, a method of dealing with anomalies in an output signalis provided. The method includes monitoring transitions in the outputsignal. When transitions do not occur at expected times, the methoddetects an anomalous signal. Determining the type of anomalous signalbased at least in part on the time period of the anomalous signal andconditioning the output signal based on the type of anomalous signaldetected.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention can be more easily understood and furtheradvantages and uses thereof more readily apparent, when considered inview of the detailed description and the following figures in which:

FIG. 1 is a block diagram of a signal correcting system of oneembodiment of the present invention is provided;

FIG. 2 is a flow diagram of a method of correcting an anomalous signalof one embodiment of the present invention;

FIG. 3 is a signal diagram illustration an anomalous signal and acorrected signal of one embodiment of the present invention.

In accordance with common practice, the various described features arenot drawn to scale but are drawn to emphasize specific features relevantto the present invention. Reference characters denote like elementsthroughout Figures and text.

DETAILED DESCRIPTION

In the following detailed description, reference is made to theaccompanying drawings, which form a part hereof, and in which is shownby way of illustration specific embodiments in which the inventions maybe practiced. These embodiments are described in sufficient detail toenable those skilled in the art to practice the invention, and it is tobe understood that other embodiments may be utilized and that logical,mechanical and electrical changes may be made without departing from thespirit and scope of the present invention. The following detaileddescription is, therefore, not to be taken in a limiting sense, and thescope of the present invention is defined only by the claims andequivalents thereof.

Embodiments of the present invention provide a method that detects andcorrects (or conditions) anomalous signals that is transparent to asystem using the signals. Referring to FIG. 1, a system 100 including asignal correcting device 104 of one embodiment of the present inventionis illustrated. The system 100 includes a signal generator 102, a signalusing device 106 and the signal correcting device 104. Although, anytype of signal generator 102 and signal using device could be used withthis invention an example of a signal generator 102 is an accelerometerand an example of the signal using device 106 is a navigation system.

The signal correcting device 104 includes a signal processor 108 and aregister 110. As illustrated the signal processor 108 is coupled toreceive an output of the signal generator 102 via input port 118. Thesignal processor 108 monitors the output signal for anomalous signals.When a anomalous signal is detected it is either skipped or replaced.The signal processor 108 then sends the corrected (or conditioned)signal to the register 110. Once the signal using device 106 is ready toprocess the signal from the signal generator 102, the signal in theregister 110 is passed on to the signal using device 106 via output port120. The signal processor 108 is able to correct anomalous signalswithout the signal using device 106 knowing of the correction becausethe signal processor 108 operates at faster speed than the signal usingdevice 106. This allows the signal correcting device 104 to have time tocorrect an anomalous signals.

In embodiments of the present invention, anomalous signals are sortedinto different types. The types of anomalous signals include signalsdesignated as either a glitch or a bursting anomaly. A glitch is a typeof anomalous signal that only occurs for relatively short period oftime. In embodiments of the present invention the relatively shortperiod of time is user defined. This select time period is dependant onthe application. In particular in some embodiments, a glitch durationvariable is loaded into the signal correcting device 104, via input port116, to be used by the signal processor 108. The glitch durationvariable sets the select period of time. An example of a detected glitchis where a transition is encountered at a time that would be outside therange of frequency but the next transition occurs at an expected timewithin the frequency range. A bursting signal is a type of anomaloussignal that occurs over a relatively long period of time. That is,bursting signals are glitches that occur continuously for a selectperiod of time based on the type of signal generator. The burstingduration is a variable that is loaded into the signal correcting device104. The signal processor 108 tracks glitches and bursting with acounter circuit 114. The counter circuit 114 includes one or morecounters. In one embodiment, a counter in the counter circuit 114 is setwhen a transition does or does not occur when expected. As discussed,the processor then uses the counter to determine the period of time ofthe anomalous signal. If the anomalous signal returns back to itsexpected frequency before the end of the select period of time, a glitchhas been detected. If a series of Glitch transitions occur beyond theselect period of time, a burst has been detected. Once the signal hasreturned to it expected frequency the counter is reset.

In some embodiments, the signal correcting device 104 tracks glitch andbursting events. This information can then be sent to an exteriorprocessor for processing. In one embodiment, a discrete register 112 isused as illustrated in FIG. 1. The signal processor 108 in the signalcorrecting device reports all occurrence of glitch rejections and alloccurrence of level transition timeout used during bursting to discreteregister 112. As illustrated, in this embodiment, an output of register112 is used by the signal using device 106 for further conditioning.

A signal processing flow diagram 200 of one method of implementing anembodiment of the present invention is illustrated in FIG. 2. Asillustrated, the method starts by monitoring the output signal of asignal generator (202). The output signal is monitored for an anomaloussignal (204). In one embodiment, this is done by monitoring thefrequency of the output signal from the signal generator 102. Dependingon the application, a normal frequency range is selected. In thisembodiment, it is determined if the frequency of the output signal iswithin the normal frequency range. The frequency is determined in oneembodiment by counting the number of transitions between states in thesignal within a given time period. If the frequency of the output signalof the signal generator 102 is outside the frequency range an anomaloussignal has been detected. If an anomalous signal is detected (204), thetype of anomalous signal is determined (206).

If the anomalous signal is determined to be a glitch (206), theanomalous portion is simply thrown out by the signal processor (210). Asdiscussed above, since, the signal generator 102 has a higher frequencythan the signal using device 106, the removal of the glitch will not benoticed by the signal using device 106. Once the anomalous glitch signalis thrown out (210), the output signal is again monitored at (202). Ifthe anomalous signal is determined to be bursting (206), the burstingportion of the signal is replaced or reconstructed (216). There are manydifferent ways in which the signal can be reconstructed. For example inone embodiment a programmed replacement signal is simply used. That is,in the embodiment, a signal of a select frequency is pre-programmed inand used to replace the bursting signal. In another embodiment, thesignal processor 108 uses a signal having a frequency that that wasoccurring right before bursting was detected. In still anotherembodiment where a signal output generator 102 outputs more than oneoutput signal and the output signals have a proportional relation, asecond non-anomalous signal is used to create a replacement signal.Other methods of generating a signal to replace an anomalous signal arecontemplated and the above are given by way of example not by way oflimitation. The reconstructed signal is then placed in the register(218). Moreover, during a bursting signal, the signal correcting device104 reconstructs the signal generators output by enabling a transitionfrom the existing level state of the signal after a timeout durationfrom a previous transition.

Embodiments of the present invention then determine when the burstinghas ended (220). If it has not ended (218), the signal processorcontinues to reconstruct the signal at (216). When it is determined thebursting has ended 220, the process continues at (202) where the outputsignal is continued to be monitored (202) and placed in the register(212) if no other anomalous signals have been detected (204). Inparticular, the signal is monitored to determine when the bursting hasended (220). Once the bursting has ended, the reconstructed signal isstopped and the output signal is transitioned back into the signalstream such that the replacement is transparent to the signal usingdevice 106. In particular, a transition is coincident with the actualsignal level change following a timeout.

Referring to FIG. 3, an example of an anomalous signal 304 and areplacement signal 302 is illustrated. In particular, signal 304represents a signal from a signal generator, such as an accelerometerthat is communicated to the signal correcting device 104. Signal 302represents a reconfigured signal that would be output from the signalcorrecting device 104 and used by the signal using device 106. Inregards to the anomalous signal 304, glitches 306 and 308 as well asbursting 310 are shown. As illustrated, the glitches 304, 306 and 308are replaced in signal 302 with the signal correcting device 104 of thepresent invention. FIG. 3 also illustrates, that the transition edgesare not aligned with respect to anomalous signal 304 and the replaced orcorrected signal 302. The shift in transition edges reflects the timeused to analysis and correct the signal.

The methods and techniques described here may be implemented in digitalelectronic circuitry, or with a programmable processor (for example, aspecial-purpose processor or a general-purpose processor such as acomputer) firmware, software, or in combinations of them. Apparatusembodying these techniques may include appropriate input and outputdevices, a programmable processor, and a storage medium tangiblyembodying program instructions for execution by the programmableprocessor. A process embodying these techniques may be performed by aprogrammable processor executing a program of instructions to performdesired functions by operating on input data and generating appropriateoutput. The techniques may advantageously be implemented in one or moreprograms that are executable on a programmable system including at leastone programmable processor coupled to receive data and instructionsfrom, and to transmit data and instructions to, a data storage system,at least one input device, and at least one output device. Generally, aprocessor will receive instructions and data from a read-only memoryand/or a random access memory. Storage devices suitable for tangiblyembodying computer program instructions and data include all forms ofnon-volatile memory, including by way of example semiconductor memorydevices, such as EPROM, EEPROM, and flash memory devices; magnetic diskssuch as internal hard disks and removable disks; magneto-optical disks;and DVD disks. Any of the foregoing may be supplemented by, orincorporated in, specially-designed application-specific integratedcircuits (ASICs) or a field programmable gate array (FPGA).

Although specific embodiments have been illustrated and describedherein, it will be appreciated by those of ordinary skill in the artthat any arrangement, which is calculated to achieve the same purpose,may be substituted for the specific embodiment shown. This applicationis intended to cover any adaptations or variations of the presentinvention. Therefore, it is manifestly intended that this invention belimited only by the claims and the equivalents thereof.

1. A method of dealing with anomalous outputs of a device, the methodcomprising: detecting anomalous signals from the first device;correcting the anomalous signals; and outputting the corrected signals,wherein correcting the signals is transparent to a second devicereceiving the outputted corrected signals.
 2. The method of claim 1,wherein detecting anomalous signals further comprises: detectingglitches, wherein a glitch is a disturbance over a relatively shortperiod of time; and detecting bursting, wherein bursting is adisturbance over a relatively extended period of time.
 3. The method ofclaim 2, wherein detecting glitches further comprises: detecting atransition edge in a signal from the first device; using a clock todetermine when the next transition edge should occur; when a transitionedge does not occur within a selected time, waiting for a subsequenttransition edge; and when a subsequent transition edge is detected,outputting the transition edge.
 4. The method of claim 2, furthercomprising: defining the relatively short period of time.
 5. The methodof claim 2, wherein correcting the anomalous signals further comprises:when detecting a glitch, removing the glitch.
 6. The method of claim 4,wherein removing the glitch further comprises: placing a next validtransition in a register to be output instead of the detected glitch. 7.The method of claim 2, wherein correcting the anomalous signals furthercomprises: when detecting a bursting, reconstructing the anomaloussignal to an expected signal.
 8. The method of claim 7, furthercomprising: placing the reconstructed signal in a register to be output.9. A method of dealing with anomalies in an output signal, the methodcomprising: monitoring transitions in the output signal; whentransitions do not occur at expected times, detecting an anomaloussignal; determining the type of anomalous signal based at least in parton the time period of the anomalous signal; and conditioning the outputsignal based on the type of anomalous signal detected.
 10. The method ofclaim 9, wherein determining the time period of the anomalous signalfurther comprises: starting a counter at the start of the detectedanomalous signal; and reading a value of the counter.
 11. The method ofclaim 9, wherein determining the type of anomalous signal furthercomprises: designating the type of anomalous signal as a glitch if theanomalous signal last for less than a select period of time; anddesignating the type of anomalous signal as bursting if glitches lastfor more than a select period of time.
 12. The method of claim 11,further comprising: defining the select period of time for Glitch andBurst detection.
 13. The method of claim 11, wherein conditioning theoutput signal based on the type of anomalous signal detected furthercomprises: when the type of anomalous signal is a designated as aglitch, removing the anomalous signal portion from the output signal;and when the type of anomalous signal is a designated as bursting,replacing the anomalous signal portion of the output signal with areconstructed signal.
 14. The method of claim 13, wherein replacing theanomalous signal portion of the output signal further comprises at leastone of; using a reconstructed signal with a programmed frequency, usinga signal having a frequency that occurred right before detection of theanomalous signal, and using a signal based off of a second differentoutput signal that has a proportional relationship to the output signal.15. A signal conditioning device, the device comprising: a signalprocessor configured to process an output signal from a signalgenerator, the signal processor further configured to detect anomalousportions of the output signal, the signal processor further adapted todetermine a type of anomalous signal detected and process the anomalousportion based on a determined type of anomalous signal; and an outputregister configured to store and output the output signal to a signalusing device, the output register further configured to store the outputsignal from the signal processor.
 16. The device of claim 15, whereinthe signal processor is configured to determine glitch anomalous signalsthat last for a relatively short user defined period of time and burstanomalous signals that are Glitches that occur continuously for a userdefined period of time, the signal processor further configured to throwout glitch portions of an anomalous signal and reconstruct burstingportions of the an anomalous signal.
 17. The device of claim 15, furthercomprising: a counter circuit having at least one counter, the at leastone counter configured to time anomalous portions of the output signalfor the signal processor.
 18. The device of claim 15, furthercomprising: a discrete register configured to track and outputoccurrences of anomalous portions of the output signal for furtherconditioning by the Signal Processing Device.
 19. The device of claim15, further comprising: an instruction port in communication with thesignal processor, the input port configured to convey instructions tothe signal processor relating to user defined periods that define thetype of anomalous signals.
 20. The device of claim 15 furthercomprising: an input port configured to receive an output signal fromthe signal generator, the input port in communication with the signalprocessor; and an output port configured to output the output signalfrom the register.